Head coach Matt Maynard admits Glamorgan performed well below par after Gloucestershire reached 168/1 at the close of play on a rain interrupted day in Bristol.
The Welsh county opted to bowl first in helpful bowling conditions, however an opening stand of 127 between Chris Dent and Miles Hammond thwarted the Glamorgan attack before captain David Lloyd made the breakthrough after an improved bowling display post lunch.
"I think our opening spell was pretty good, but our lines and lengths were so much better after lunch," said Maynard.
"They scored far too much off the back foot in that first session, though credit to Dent and Hammond, they played very well and got through the new ball.
"We weren't at our best, but I thought we bowled really well after lunch with Lloyd bowling wicket-to-wicket and Hoges (Michael Hogan) bowling well.
"We knew the pitch would be slow after the (wet) weather they've had, but we expected it to do a bit more than it did.
"It was the right decision (to bowl first), but we didn't execute as well as we could have done and two catches going down at slip didn't help our cause either, poor old Marchant (de Lange) has had seven catches dropped at slip this year, all left-handers."