Dillon Pennington claimed a wicket on his Second Eleven debut for Worcestershire on a day dominated by the Gloucestershire batsmen at Cheltenham College.
Academy product Pennington struck an early blow when he had Brandon Gilmour (1) caught at square leg by Adam Finch with just seven runs on the board.
He finished the day with the creditable figures of 1-33 from 13 overs, four of which were maidens.
Gloucestershire were 89-3 at one stage after electing to bat with Finch bowling Cameron Bancroft (36) while skipper Ian Cockbain (13) holed out to Ollie Westbury at short mid on off Alex Hepburn.
But the remainder of the day was dominated by home keeper Gareth Roderick who made 170 off 222 balls with one six and 23 fours.
He shared in a fourth wicket stand of 89 with Graeme van Buuren (37) and then 154 in 32 overs for the fifth with George Hankins (74).
Roderick was eventually caught and bowled by Zen Malik who also dismissed Hankins with Ben Twohig taking a fine diving catch at deep mid off.
Kieran Noema Barnett (56) and Mike Hammond then added 82 for the seventh wicket before the former provided Finch with a second success after holing out to Hepburn at mid off.
Gloucestershire closed the first day of the three-day fixture on 455-7 from 104 overs.
Gloucestershire Seconds – first innings
CT Bancroft b AW Finch 36
BS Gilmour c AW Finch b D Pennington 1
GH Roderick+ c and b Z Ul-A Malik 170
IA Cockbain* c OE Westbury b A Hepburn 13
GL van Buuren c GH Rhodes b PR Brown 37
GT Hankins c BJ Twohig b Z Ul-A Malik 74
K Noema-Barnett c A Hepburn b AW Finch 56
MAH Hammond not out 40
GS Drissell not out 20
Total (for 7 wickets) 455 in 104 overs
FOW: 7, 68, 89, 178, 332, 342, 424
PR Brown 15-0-73-1
D Pennington 13-4-33-1
A Hepburn 20-3-64-1
AW Finch 13-0-69-2
BJ Twohig 15-1-90-0
GH Rhodes 12-0-58-0
RA Whiteley 6-0-23-0
Z Ul-A Malik 8-1-33-2