Westfield Capital Management Co. LP

Q2 2026Q1 2026Q4 2025Q3 2025Q2 2025Q1 2025Q4 2024Q3 2024Q2 2024

In its 13F for Q1 2024 (holdings as of March 31, 2024, filed May 10, 2024), Westfield Capital Management Co. LP reported 244 stock positions worth $19.0 billion. Its top holding was Microsoft (MSFT) at 3.4% of the portfolio, followed by Ascendis Pharma A/S (ASND, 3.2%) and Apple (AAPL, 2.9%). Compared with Q4 2023, it opened 30 new positions, sold out of 25, added to 83 and reduced 118. The biggest buy was Nvidia (NVDA, shares +1%) and the biggest sale Marvell Technology (MRVL, shares −99%).

Most Recent 13F: Q2 2026
Location: BOSTON, MA
CIK: 0001177719
Portfolio Value: $19.0B (Q1 2024)
SEC Filing: 0001085146-24-002397 ↗ filed May 10, 2024

Holdings Value

Holdings 244 stocks · $19.0B


MSFT Microsoft Corp.	3.36%	1,522,930	$640.7M	Reduce -2.2%
ASND Ascendis Pharma A/S	3.23%	4,075,214	$616.1M	Add +1.1%
AAPL Apple Inc.	2.91%	3,237,247	$555.1M	Add +29.9%
NVDA Nvidia Corp.	2.85%	599,967	$542.1M	Add +0.7%
AMZN Amazon.com Inc.	2.49%	2,633,433	$475.0M	Add +12.8%
GOOGL Alphabet Inc. Class A	2.34%	2,956,626	$446.2M	Reduce -9.0%
TDG Transdigm Group Inc.	2.04%	315,374	$388.4M	Reduce -1.5%
META Meta Platforms Inc. Class A	1.79%	702,584	$341.2M	Reduce -3.0%
BLDR Builders Firstsource Inc.	1.51%	1,381,284	$288.1M	Reduce -2.5%
V Visa Inc. Class A	1.49%	1,019,994	$284.7M	Reduce -6.1%
VRT Vertiv Holdings Co. Class A	1.46%	3,399,272	$277.6M	Add +85.2%
AXON Axon Enterprise Inc.	1.17%	709,306	$221.9M	Reduce -3.1%
NOW ServiceNow Inc.	1.13%	281,388	$214.5M	Reduce -5.0%
DXCM Dexcom Inc.	1.12%	1,539,461	$213.5M	Reduce -17.1%
FIX Comfort Systems USA Inc.	1.11%	667,036	$211.9M	Add +56.4%
UNH Unitedhealth Group Inc.	1.11%	426,637	$211.1M	Reduce -1.9%
ICLR Icon PLC	0.95%	536,883	$180.4M	Reduce -3.9%
CRM Salesforce Inc.	0.93%	590,564	$177.9M	Reduce -2.9%
AME Ametek Inc.	0.92%	953,603	$174.4M	Reduce -2.7%
OPCH Option Care Health Inc.	0.91%	5,171,385	$173.4M	Add +15.4%
MHO M/I Homes Inc.	0.87%	1,219,989	$166.3M	Add +3.0%
LECO Lincoln Electric Holdings	0.87%	646,442	$165.1M	Reduce -6.0%
ABBV Abbvie Inc.	0.85%	887,179	$161.6M	Add +5.7%
CSGP Costar Group Inc.	0.84%	1,647,389	$159.1M	Add +17.8%
SAIA Saia Inc.	0.80%	259,082	$151.6M	Reduce -31.2%
NICE Nice Ltd. - Spon ADR	0.78%	571,436	$148.9M	Reduce -1.4%
HD Home Depot Inc.	0.75%	374,807	$143.8M	Reduce -1.8%
UBER Uber Technologies Inc.	0.71%	1,767,673	$136.1M	Reduce -0.5%
AVTR Avantor Inc.	0.70%	5,244,215	$134.1M	Reduce -3.2%
WSC Willscot Holdings Corp.	0.67%	2,752,063	$128.0M	Add +1.2%
PGR Progressive Corp.	0.67%	617,410	$127.7M	Add +7.0%
LEGN Legend Biotech Corp.-ADR	0.66%	2,239,774	$125.6M	Add +26.1%
CPRT Copart Inc.	0.66%	2,167,032	$125.5M	Add +19.1%
COST Costco Wholesale Corp.	0.65%	169,256	$124.0M	Reduce -8.6%
LNTH Lantheus Holdings Inc.	0.64%	1,958,018	$121.9M	Add +25.3%
HUBS HubSpot Inc.	0.64%	194,437	$121.8M	Add +1.3%
FLYW Flywire Corp.-Voting	0.63%	4,837,491	$120.0M	Add +10.3%
TSM Taiwan Semiconductor-SP ADR	0.61%	854,438	$116.2M	New
STZ Constellation Brands Inc. Class A	0.61%	427,161	$116.1M	Reduce -1.9%
INSP Inspire Medical Systems Inc.	0.61%	538,294	$115.6M	Reduce -1.3%
GPN Global Payments Inc.	0.61%	863,745	$115.4M	Reduce -0.4%
CDNS Cadence Design SYS Inc.	0.61%	370,675	$115.4M	Reduce -3.3%
WING Wingstop Inc.	0.61%	314,818	$115.3M	Add +25.9%
TXRH Texas Roadhouse Inc.	0.60%	740,719	$114.4M	Reduce -3.6%
MGM MGM Resorts International	0.59%	2,362,356	$111.5M	Reduce -1.6%
PCVX Vaxcyte Inc.	0.57%	1,586,095	$108.3M	Add +9.0%
RCKT Rocket Pharmaceuticals Inc.	0.56%	3,984,030	$107.3M	Add +1.1%
AIG American International Group	0.56%	1,366,011	$106.8M	Reduce -1.1%
CMG Chipotle Mexican Grill Inc.	0.56%	36,567	$106.3M	Reduce -8.1%
ROST Ross Stores Inc.	0.56%	721,370	$105.9M	Reduce -2.2%
UNP Union Pacific Corp.	0.55%	422,492	$103.9M	Add +3.4%
LPLA LPL Financial Holdings Inc.	0.53%	385,227	$101.8M	Reduce -10.2%
MASI Masimo Corp.	0.53%	686,100	$100.8M	Reduce -16.2%
AVY Avery Dennison Corp.	0.53%	450,289	$100.5M	Reduce -3.8%
APO Apollo Global Management Inc.	0.52%	886,761	$99.7M	Add +9.8%
ITT Itt Inc.	0.52%	723,617	$98.4M	Add +12.5%
FFIV F5 Inc.	0.51%	515,507	$97.7M	Reduce -8.6%
FICO Fair Isaac Corp.	0.51%	77,370	$96.7M	Reduce -2.1%
WDAY Workday Inc. Class A	0.50%	352,536	$96.2M	Reduce -6.3%
MNDY Monday.com Ltd.	0.49%	415,584	$93.9M	Add +33.0%
HUBB Hubbell Inc.	0.49%	225,547	$93.6M	Reduce -20.6%
IDXX Idexx Laboratories Inc.	0.49%	172,021	$92.9M	Add +6.8%
NXPI NXP Semiconductors NV	0.49%	374,539	$92.8M	Add +974.4%
SMAR Smartsheet Inc. Class A	0.48%	2,386,272	$91.9M	Reduce -11.8%
DKNG Draftkings Inc. Class A	0.48%	2,007,587	$91.2M	Add +19.0%
DT Dynatrace Inc.	0.47%	1,923,414	$89.3M	Reduce -1.2%
CE Celanese Corp.	0.47%	519,641	$89.3M	Reduce -0.6%
ROK Rockwell Automation Inc.	0.47%	304,384	$88.7M	Reduce -2.3%
PTC PTC Inc.	0.46%	467,231	$88.3M	Reduce -4.2%
FOUR SHIFT4 Payments Inc. Class A	0.46%	1,333,252	$88.1M	Add +72.8%
IEX Idex Corp.	0.46%	359,880	$87.8M	Reduce -3.0%
ARES Ares Management Corp. Class A	0.45%	649,344	$86.3M	Reduce -1.5%
MTH Meritage Homes Corp.	0.45%	490,660	$86.1M	Add +13.5%
JBHT Hunt (jb) Transprt SVCS Inc.	0.45%	431,427	$86.0M	Reduce -1.6%
CDW CDW Corp.	0.45%	334,332	$85.5M	Reduce -11.4%
OWL Blue Owl Capital Inc.	0.45%	4,529,065	$85.4M	Add +6.5%
VMC Vulcan Materials Co.	0.45%	311,381	$85.0M	Reduce -2.2%
MSCI MSCI Inc.	0.44%	150,518	$84.4M	Add +1.6%
IOT Samsara Inc. Class A	0.44%	2,228,759	$84.2M	Add +12.3%
CSCO Cisco Systems Inc.	0.44%	1,686,503	$84.2M	Add +825.1%
CWST Casella Waste Systems Inc. Class A	0.44%	848,012	$83.8M	Add +12.8%
MKSI MKS Inc. filed as MKS INSTRS INC	0.43%	620,063	$82.5M	Add +5.2%
HLT Hilton Worldwide Holdings Inc.	0.42%	379,064	$80.9M	Reduce -2.2%
PODD Insulet Corp.	0.42%	468,320	$80.3M	Reduce -33.6%
PR Permian Resources Corp. Class A	0.42%	4,541,934	$80.2M	Reduce -4.3%
BIO Bio-Rad Laboratories-A	0.42%	230,509	$79.7M	Reduce -6.8%
MDB Mongodb Inc.	0.42%	221,858	$79.6M	Add +50.5%
RRR Red Rock Resorts Inc. Class A	0.42%	1,328,200	$79.5M	Reduce -4.2%
COO The Cooper Cos Inc.	0.41%	776,971	$78.8M	Add +9.6%
SUI Sun Communities Inc. filed as SUN CMNTYS INC	0.41%	604,004	$77.7M	Reduce -3.6%
NSIT Insight Enterprises Inc.	0.39%	405,407	$75.2M	Add +28.0%
AZEK The Azek Co. Inc.	0.39%	1,487,700	$74.7M	Add +1.7%
HXL Hexcel Corp.	0.39%	1,018,276	$74.2M	Reduce -27.4%
AJG Arthur J Gallagher & Co. filed as GALLAGHER ARTHUR J & CO	0.38%	291,382	$72.9M	Reduce -21.0%
PCOR Procore Technologies Inc.	0.38%	880,442	$72.3M	Add +1.1%
OVV Ovintiv Inc.	0.38%	1,385,002	$71.9M	Reduce -4.3%
BFAM Bright Horizons Family Solut	0.38%	631,590	$71.6M	Reduce -4.0%
ZS Zscaler Inc.	0.37%	368,283	$70.9M	Reduce -10.6%
NOG Northern Oil and Gas Inc.	0.36%	1,749,749	$69.4M	Add +13.8%
NBIX Neurocrine Biosciences Inc.	0.36%	503,193	$69.4M	Reduce -15.3%

Show all 244 holdings

Portfolio Sells Q4 2023 → Q1 2024


MRVL Marvell Technology Inc.	Reduce -98.8%	0.01%	−0.84
PODD Insulet Corp.	Reduce -33.6%	0.42%	−0.47
LLY Eli Lilly & Co.	Reduce -83.2%	0.12%	−0.46
MCD McDonald's Corp.	Sold out	0.00%	−0.45
PPG PPG Industries Inc.	Sold out	0.00%	−0.44
WSO Watsco Inc.	Reduce -88.4%	0.05%	−0.40
DOO BRP Inc./Ca- Sub Voting	Sold out	0.00%	−0.37
S Sentinelone Inc. Class A	Sold out	0.00%	−0.37
G Genpact Ltd.	Reduce -48.6%	0.27%	−0.34
GOOGL Alphabet Inc. Class A	Reduce -9.0%	2.34%	−0.30
POOL Pool Corp.	Sold out	0.00%	−0.29
SMAR Smartsheet Inc. Class A	Reduce -11.8%	0.48%	−0.27
MCHP Microchip Technology Inc.	Reduce -79.2%	0.06%	−0.27
OKTA Okta Inc.	Sold out	0.00%	−0.26
P Everpure Inc. Class A	Sold out	0.00%	−0.26
TENB Tenable Holdings Inc.	Reduce -51.4%	0.21%	−0.24
AAON Aaon Inc.	Reduce -98.3%	0.00%	−0.23
TRU Transunion	Sold out	0.00%	−0.23
UNH Unitedhealth Group Inc.	Reduce -1.9%	1.11%	−0.23
TSLA Tesla Inc.	Reduce -14.8%	0.27%	−0.23
BAH Booz Allen Hamilton Holdings	Sold out	0.00%	−0.22
PCTY Paylocity Holding Corp.	Reduce -44.5%	0.24%	−0.22
DXCM Dexcom Inc.	Reduce -17.1%	1.12%	−0.22
HXL Hexcel Corp.	Reduce -27.4%	0.39%	−0.21
AMP Ameriprise Financial Inc.	Reduce -82.3%	0.04%	−0.20
KLIC Kulicke & Soffa Industries	Sold out	0.00%	−0.20
CERE Cerevel Therapeutics Holding	Sold out	0.00%	−0.19
TPR Tapestry Inc.	Reduce -49.8%	0.26%	−0.19
PANW Palo Alto Networks Inc.	Reduce -37.8%	0.21%	−0.18
LSCC Lattice Semiconductor Corp.	Sold out	0.00%	−0.18
LITE Lumentum Holdings Inc.	Sold out	0.00%	−0.17
EWBC East West Bancorp Inc.	Reduce -42.3%	0.23%	−0.17
SAIA Saia Inc.	Reduce -31.2%	0.80%	−0.17
ACLS Axcelis Technologies Inc.	Sold out	0.00%	−0.16
ZS Zscaler Inc.	Reduce -10.6%	0.37%	−0.16
V Visa Inc. Class A	Reduce -6.1%	1.49%	−0.15
DT Dynatrace Inc.	Reduce -1.2%	0.47%	−0.15
FIVE Five Below	Reduce -4.3%	0.36%	−0.13
SPGI S&P Global Inc.	Reduce -19.2%	0.28%	−0.12
AVGO Broadcom Inc.	Reduce -45.1%	0.17%	−0.12
HLIT Harmonic Inc.	Sold out	0.00%	−0.11
DAY Dayforce Inc.	Reduce -14.9%	0.35%	−0.11
DECK Deckers Outdoor Corp.	Reduce -44.0%	0.25%	−0.10
AJG Arthur J Gallagher & Co.	Reduce -21.0%	0.38%	−0.10
WDAY Workday Inc. Class A	Reduce -6.3%	0.50%	−0.10
ROK Rockwell Automation Inc.	Reduce -2.3%	0.47%	−0.10
CBAY Cymabay Therapeutics Inc.	Sold out	0.00%	−0.10
NOW ServiceNow Inc.	Reduce -5.0%	1.13%	−0.09
NBIX Neurocrine Biosciences Inc.	Reduce -15.3%	0.36%	−0.09
ST Sensata Technologies Holdplc	Reduce -17.2%	0.24%	−0.09

Portfolio Buys Q4 2023 → Q1 2024


NVDA Nvidia Corp.	Add +0.7%	2.85%	+1.13
VRT Vertiv Holdings Co. Class A	Add +85.2%	1.46%	+0.94
TSM Taiwan Semiconductor-SP ADR	New	0.61%	+0.61
FIX Comfort Systems USA Inc.	Add +56.4%	1.11%	+0.60
NXPI NXP Semiconductors NV	Add +974.4%	0.49%	+0.44
AMZN Amazon.com Inc.	Add +12.8%	2.49%	+0.43
CSCO Cisco Systems Inc.	Add +825.1%	0.44%	+0.39
COHR Coherent Corp.	New	0.36%	+0.36
ONON On Holding AG Class A	New	0.35%	+0.35
MSTR Strategy Inc.	New	0.32%	+0.32
SAP Sap SE-Sponsored ADR	New	0.31%	+0.31
IRTC Irhythm Holdings Inc.	New	0.31%	+0.31
SIGI Selective Insurance Group	New	0.29%	+0.29
VKTX Viking Therapeutics Inc.	New	0.28%	+0.28
ASND Ascendis Pharma A/S	Add +1.1%	3.23%	+0.28
FLEX Flex Ltd.	New	0.27%	+0.27
CYTK Cytokinetics Inc.	New	0.27%	+0.27
GTLB Gitlab Inc. Class A	New	0.26%	+0.26
DSGX The Descartes Systems Grp	New	0.25%	+0.25
WING Wingstop Inc.	Add +25.9%	0.61%	+0.23
KEY Keycorp	New	0.23%	+0.23
SMCI Super Micro Computer Inc.	Add +20.3%	0.30%	+0.22
FCNCA First Citizens Bcshs Class A	Add +770.1%	0.24%	+0.21
JBL Jabil Inc.	New	0.20%	+0.20
NVMI Nova Ltd.	New	0.20%	+0.20
LSPD Lightspeed Commerce Inc.	New	0.18%	+0.18
EXPE Expedia Group Inc.	New	0.18%	+0.18
RVLV Revolve Group Inc. Class A	New	0.18%	+0.18
MNDY Monday.com Ltd.	Add +33.0%	0.49%	+0.15
CPRT Copart Inc.	Add +19.1%	0.66%	+0.14
PGR Progressive Corp.	Add +7.0%	0.67%	+0.13
DKNG Draftkings Inc. Class A	Add +19.0%	0.48%	+0.13
FOUR SHIFT4 Payments Inc. Class A	Add +72.8%	0.46%	+0.13
CSGP Costar Group Inc.	Add +17.8%	0.84%	+0.12
AAPL Apple Inc.	Add +29.9%	2.91%	+0.12
NXT Nextpower Inc.	Add +73.3%	0.24%	+0.11
RMBS Rambus Inc.	New	0.11%	+0.11
CRDO Credo Technology Group Holdi	New	0.09%	+0.09
ABBV Abbvie Inc.	Add +5.7%	0.85%	+0.09
APO Apollo Global Management Inc.	Add +9.8%	0.52%	+0.08
MKSI MKS Inc.	Add +5.2%	0.43%	+0.08
OWL Blue Owl Capital Inc.	Add +6.5%	0.45%	+0.08
LNTH Lantheus Holdings Inc.	Add +25.3%	0.64%	+0.07
ITT Itt Inc.	Add +12.5%	0.52%	+0.07
SYNA Synaptics Inc.	New	0.07%	+0.07
NSIT Insight Enterprises Inc.	Add +28.0%	0.39%	+0.07
MDB Mongodb Inc.	Add +50.5%	0.42%	+0.07
AZEK The Azek Co. Inc.	Add +1.7%	0.39%	+0.07
RRX Regal Rexnord Corp.	Add +18.6%	0.29%	+0.07
CWST Casella Waste Systems Inc. Class A	Add +12.8%	0.44%	+0.07

All Filings

Quarter	Positions	13F Reported Value	Top Holdings
Q2 2026	278	$30.6B	NVDA, GOOGL, ASND, AXON, FTAI
Q1 2026	250	$23.8B	NVDA, ASND, FIX, AAPL, FTAI
Q4 2025	241	$24.0B	NVDA, ASND, AAPL, MSFT, GOOGL
Q3 2025	235	$23.8B	NVDA, ASND, MSFT, AAPL, FIX
Q2 2025	239	$23.8B	NVDA, ASND, MSFT, AAPL, AMZN
Q1 2025	244	$20.5B	ASND, NVDA, AAPL, MSFT, AMZN
Q4 2024	239	$23.0B	NVDA, AAPL, MSFT, ASND, AMZN
Q3 2024	247	$22.1B	NVDA, AAPL, MSFT, ASND, AMZN
Q2 2024	248	$20.4B	NVDA, MSFT, AAPL, ASND, AMZN
Q1 2024	244	$19.0B	MSFT, ASND, AAPL, NVDA, AMZN