generate
  for(i=1; i<=num_duts; i++)
  begin: generate_my_oscillators
    osc osc_c_osc( .en(osc_en[i]), .out(osc_c[i]));
  end
endgenerate

foreach(OSC_PER[i])
  generate_my_oscillators[i].osc_c_osc.per = OSC_PER[i];

generate_my_oscillators[1].osc_c_osc.per = OSC_PER[1]
if(number_devices >= 2)
generate_my_oscillators[2].osc_c_osc.per = OSC_PER[2]
if(number_devices >= 3)
generate_my_oscillators[3].osc_c_osc.per = OSC_PER[3]
.
.
.

generate
  for(i=1; i<=num_duts; i++)
  begin: generate_my_oscillators
    osc osc_c_osc( .en(osc_en[i]), .out(osc_c[i]));
    .per = OSC_PER[i];
  end
endgenerate

generate
  for(i=1; i<=num_duts; i++)
  begin: generate_my_oscillators
    osc osc_c_osc( .en(osc_en[i]), .out(osc_c[i]));
    osc_c_osc.per = OSC_PER[i];
  end
endgenerate

generate
  for(i=1; i<=num_duts; i++)
  begin: generate_my_oscillators
    osc osc_c_osc( .en(osc_en[i]), .out(osc_c[i]), .per(OSC_PER[i]);
  end
endgenerate

generate
for(i=1; i<=num_duts; i++) begin: generate_my_oscillators
  osc #( .per(OSC_PER[i]) ) osc_c_osc( .en(osc_en[i]), .out(osc_c[i]) );
end
endgenerate

generate
for(i=1; i<=num_duts; i++) begin: generate_my_oscillators
  osc osc_c_osc( .en(osc_en[i]), .out(osc_c[i]) );
  defparam osc_c_osc.per = OSC_PER[i];
end
endgenerate

generate
for(i=1; i<=num_duts; i++) begin: generate_my_oscillators
  osc osc_c_osc( .en(osc_en[i]), .out(osc_c[i]) );
  // Pick one based on the type of per and OSC_PER
  //assign osc_c_osc.per = OSC_PER[i]; // per is a wire
  //initial osc_c_osc.per = OSC_PER[i]; // per is non-wire and OSC_PER is a constant
  //always @* osc_c_osc.per = OSC_PER[i]; // per & OSC_PER are non-wire variables
end
endgenerate