a group of campers lakeside, preparing and barbecuing food
the bvoy was dressed as a cowboy
These two sentences are not related, a bvoy dressed as a cowboy doesn't have to do with campers.
exists e1 e2 x1 x2 x3 x4 x5 x6 x7 x8.(Theme(e2,x8) & Actor(e2,x5) & v_barbecue(e2) & n_food(x8) & of(x5,x6) & n_lakeside(x6) & of(x6,x7) & n_camper(x7) & n_group(x5) & Theme(e1,x4) & Actor(e1,x1) & v_prepare(e1) & n_food(x4) & of(x1,x2) & n_lakeside(x2) & of(x2,x3) & n_camper(x3) & n_group(x1))
exists e1 x1 x2.(n_bvoy(x1) & as(e1,x2) & n_cowboy(x2) & Theme(e1,x1) & v_dress(e1))